Since your Skype account is already a Microsoft account, it is not possible to merge or unlink your Skype and Microsoft account.
With your account you will have access to sign in to all your Microsoft services - including Skype, Office Online, Outlook, OneNote, OneDrive, Xbox, and more. When you sign into one of the Microsoft services you may be prompted to add an email. Adding an email simply makes it easy to recover your account while adding additional security.
Having problems adding an email to your account?